The instant invention relates to single-lever engine throttle and transmission control devices used on water craft to allow single or multiple station operator control over the rotational direction and speed of a driven propeller.
The life of a transmission used in marine applications is severely reduced when its gears are engaged or disengaged at engine speeds above "idle." Hence, the recommended practice is to adjust the engine throttle to the idle position prior to "shifting" the transmission. The prior art teaches the use of single- and dual-lever engine throttle/transmission control devices to allow remote operator control of engine throttle and transmission settings. With a dual-lever system, the throttle and transmission are operated independently, each with its own control lever. Hence, in order to prevent transmission damage the operator must remember to return the throttle lever to the idle position prior to engagement or disengagement of the transmission. In contrast, with the single-lever design, by moving the actuator lever in a first direction, usually forward toward the bow of the vessel, the operator first engages the transmission in "forward," and then increases engine speed proportionally to such forward lever movement. When the operator attempts to return to neutral transmission position, he must first move the single lever back through idle throttle before the single-lever mechanism will disengage the transmission. Similarly, in moving the control lever aft, the transmission is first engaged in "reverse," only then to be followed by increasing engine throttle. And, again, when returning to neutral transmission from the condition of reverse with throttle up, the operator automatically reduces throttle to the idle position prior to disengagement of the transmission. Thus, the single-lever control system automatically ensures idle throttle when shifting.
There is frequently the need to provide engine throttle and transmission control from two or more stations, with each lever moving in sync with the corresponding lever of the other stations. Additionally, to be successful in the marketplace, an engine throttle and transmission control system must incorporate means to increase engine throttle while the transmission remains in "neutral" to facilitate engine starting and warm-up.
The prior art teaches single- or multi-station use of single-lever electrically operated selsyns and mechanical systems employing push-pull cables. However, electrically dependent systems are particularly vulnerable to power interruptions and other electrical system malfunctions; multiple station mechanical systems employing push-pull cables are cumbersome and complicated, requiring elaborate routing schemes to properly synchronize the various control stations, as well as complicated mechanical lock-out systems to enable increased engine throttle while in neutral. Alternatively, the prior art teaches multi-station dual-lever hydraulic control systems which feature high reliability and ease of control line routing. Unfortunately, hydraulic systems are not available in the more desirable single-lever design.